This application claims the priority of German Patent No. 103 11 880.2-55, filed 17 Mar. 2003, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a radar method of classifying or identifying helicopters.
Known methods for the classification or identification of helicopters use one-dimensional distance profiles generated by radar. These are correlated with stored comparison profiles. The comparison profiles have to be generated for each helicopter type and any possible aspect angle (in the azimuth and elevation direction). For example, distance profiles for 100 discrete azimuth values (for example, from −180° to 180° in 3.6° steps) and, independently thereof, for 21 discrete elevation values (for example, from −40° to 40° in 4° steps) are generated in discrete steps. Thus, for one helicopter type, 100*21=2,100 distance profiles have to be generated and be retrievable in a data bank. When approximately 40 currently customary helicopter types are used as a basis, a total of over 82,000 distance profiles are required in order to carry out a reliable classification.
It is an object of the present invention to provide a classification method or an identification method for helicopters in which the volume of comparison data can be considerably reduced and by means of which the comparison data can be determined at low expenditures.
This task is achieved by generating a one-dimensional distance profile of the helicopter to be classified or to be identified by means of radar and determining the aspect angles in the azimuth and elevation directions relative to the axis of the radar antenna. The following radar echoes are measured in the one-dimensional distance profile:
(a) radar echo of the helicopter fuselage,
(b) radar echo of the rotor head of the main rotor and/or the radar echo of the main rotor axis,
(c) radar echo of the rear rotor axis;
The task further involves determining at least two of the following helicopter parameters from the measured radar echoes as well as the determined aspect angles:
(1) total length of the helicopter,
(2) distance between the rotor axes of the main and rear rotor,
(3) distance between the nose of the helicopter and the rotor axis of the main rotor;
Finally, the determined helicopter parameters are compared with stored helicopter parameters for different helicopter types.
Thus, no radar measuring data of helicopters is required as comparison data for the application of the invention. Only fixed helicopter parameters required as comparison data, which can be obtained from generally accessible sources, such as publications (Jane's “All the World's Aircraft”) or on the Internet (http://fas.org).
The method according to the invention can be used from a flying platform (for example, a helicopter, a combat aircraft) as well as from a stationary radar antenna platform.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.